Did Meteorite Carve Icy Antarctic Crater?

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Researchers in remote East Antarctica think a massive area of
fractured ice discovered last month could be a newfound meteorite
impact crater.

The mile-wide crater
(about 2 kilometers across) is a circular scar marked by
fractured, rumpled ice — a striking blot in this otherwise smooth
section of Antarctica's King Baudouin Ice Shelf. It was spotted
by German scientist Christian Müller during an aerial survey by
plane on Dec. 20, 2014.

"I looked out of the window, and I saw an unusual structure on
the surface of the ice," Müller said in a video describing the
discovery. "There was some broken ice looking like
icebergs, which is very unusual on a normally flat ice shelf,
surrounded by a large, wing-shaped, circular structure," said
Müller, a geoscientist with Fielax, a private company assisting
Antarctic research. [ See
a video of the Antarctic crater discovery ]

Lucky find

The possible impact crater is about twice the size of Arizona's
Barringer Meteor Crater. Satellite images suggest the
broken-up ice could be at least 25 years old.

The crater was a serendipitous find, sighted by chance north of
Belgium's Princess Elisabeth Research Station. German researchers
at the station intended to remotely survey the surrounding
bedrock, in order to gather new details on the Gondwana
supercontinent's formation and breakup between 550 million and
180 million years ago. Flying over busted-up ice shelves — the
floating extensions of the Antarctic Ice
Sheet — was not part of the research plan.

"We were only flying that far in the north because the radar
equipment had broken, and we didn't want to waste a good flying
day," said Graeme Eagles, a scientist at Germany's Alfred Wegener
Institute who is currently leading the geophysical research
survey. "It's been a tremendously exciting couple of weeks," he
added. "It really is a very raw form of science, with a lot of
people speculating on what might or might not be the cause."

At first, Müller connected the crater to a 2004 meteor blast
detected above this part of
East Antarctica. Recently, however, the German research team
discovered the crater in satellite images dating back to 1996,
Eagles said. "The [connection] to the 2004 event really piqued
our interest in the first place, but I don't think what we've
seen in the satellite images rules out the possibility of an
impact origin," Eagles told Live Science. "It just fuzzies the
story a little bit."

As a rule of thumb, an object that formed a crater is usually
about 10 to 20 times smaller than the crater itself, said Peter
Brown, director of the Center for Planetary Science and
Exploration at the University of Western Ontario in Canada. That
means a 1.2-mile (2 km) crater would result from an object that
measures roughly 325 feet (100 meters) across, Brown said.

"A very large explosion would have caused a 2-kilometer-wide
crater — much larger than anything detected impacting Earth in
recent history," Brown said. "So the feature seen is almost
certainly not due to any
meteorite impact."

Meteorite hunter Peter Jenniskens also found the crater idea
implausible. "I don't think this is an impact crater," said
Jenniskens, who holds dual affiliations at the SETI Institute and
at NASA's Ames Research Center, both in California.

However, Eagles hinted that the German researchers have not shown
all their cards. The scientists collected photos, video and data
on a Dec. 26 trip to the crater site. The team mapped the ice
surface in great detail with a laser-scanning instrument that
records precise changes in topography. They also surveyed the
area with a radar instrument that penetrates the upper surface of
the ice and snow. A number of smaller circular and subcircular
structures were spotted nearby on this trip. The researchers
haven't yet analyzed the data, but they hope to publish their
results in a scientific journal if the structure is indeed an
impact crater, Eagles said.

"This thing is very unusual indeed," Eagles said. "Extraordinary
claims require extraordinary evidence, and in this case, as far
as we can tell, is does look like it is extraordinary evidence."

Rock hunters

The researchers now must complete their Gondwana study before
squeezing in any more trips to the crater, Eagles said. For
instance, the team would like to eventually
hunt for meteorites around the site.

Antarctica's cold, dry conditions preserve meteorites that
weather away on other continents, and more than 20,000 space
rocks have been discovered in targeted searches on the frozen
surface.

While scientists do come to Antarctica specifically to hunt for
meteorites, finding a potential impact crater was an unexpected
thrill for everyone at the research station, the researchers
said. "There are new and exciting things to be discovered at any
moment, anytime, in Antarctica, and you don't have to send probes
to land on comets to make people's eyes sparkle," Eagles said.